High powder CO2 and Nd-YAG laser welding of wrought inconel 718

High power laser welding techniques and related metallurgy have been investigated on Inconel 718 sheets, 4 mm and 8 mm of thickness, in annealed and aged states. The CO2 CW laser welded joint, with high depth to width ratio, is suitable for post welding machining. The uniform bead profiles were acheived by using an Nd-YAG pulsed laser, which have an overlapping rate of about 85%. Wrought Inconel 718 can be welded by laser in both annealed and aged states, but the grain size must be ASTM 10 or finer in order to control the microffissuring. The microfissures relate to the delta phase at fine grain boudaries (ASTM 9-12) and the NbC phase at large grain boundaries (ASTM 6) in particular, which occur in the delta phase band. The eutectic of the Gamma/NbC was suppressed by rapid solidification in the fusion zone. Many delta phases precipitate at interdendrites with 960 degrees C post welding solution treatment. Above 1038 degrees C the laves phase dissolves completely and only NdC is present.